Peptidolipid as binding site of acetylcholinesterase: molecular recognition of paraoxon in Langmuir films

Hierarchical Self-Assembled Peptide Nano-ensembles

A variety of peptides can be self-assembled, i.e. self-organized spontaneously, into large and complex hierarchical structures, reproducibly by regulating a range of parameters that can be environment driven, process driven, or peptide driven. These supramolecular peptide aggregates yield different shapes and structures like nanofibers, nanotubes, nanobelts, nanowires, nanotapes, and micelles. These peptide nanostructures represent a category of materials that bridge biotechnology and nanotechnology and are found suitable not only for biomedical applications such as tissue engineering and drug delivery but also in nanoelectronics.

Designed amphiphilic β-sheet peptides as templates for paraoxon adsorption and detection

Amphiphilic peptides were designed to fold into a β-sheet monolayer structure while presenting the catalytic triad residues of the enzyme, acetylcholinesterase (Glu, His, and Ser), to a solution containing the organophosphate, paraoxon. Three peptides, in which the catalytic triad residues were arranged in different orders along the strand, were generated to reveal potential differences in interactions with paraoxon as a function of the order of these amino acids. One additional peptide with amino acids introduced in random order was studied to highlight the contribution of the β-sheet secondary structure to any interactions with paraoxon. Langmuir isotherms, Brewster angle microscope at interfaces, and circular dichroism measurements in bulk showed that both the β-sheet conformation and the order of the amino acids along the strand influenced the interactions of paraoxon with the peptides. Compression isotherm curves as well as Brewster angle microscopy images provided evidence for enhanced adsorption of the paraoxon to the monolayers of peptides, which present neighboring Glu and Ser residues along the hydrophilic face of the β-strand. Circular dichroism revealed that the peptide most sensitive to interactions with paraoxon was that with the triad residues in the order Glu, Ser, and His, which appears to be appropriate for supporting a catalytic mechanism similar to that in the acetylcholinesterase enzyme. These rationally designed peptides may be further used for the development of technologies for organophosphate adsorption and detection.

Gold Nanoparticle Based Surface Enhanced Fluorescence For Detection of Organophosphorus Agents

Organophosphorus agents (OPA) represent a serious concern to public safety as nerve agents and pesticides. Here we report the development of gold nanoparticle based surface enhanced fluorescence (NSEF) spectroscopy for rapid and sensitive screening of organophosphorus agents. Fluorescent from Eu3+ ions that are bound within the electromagnetic field of gold nanoparticles exhibit a strong enhancement. In the presence of OPA, Eu3+ ions are released from the gold nanoparticle surface and thus a very distinct fluorescence signal change was observed. We discussed the mechanism of fluorescence enhancement and the role of OPA for fluorescence intensity change in the presence of gold nanoparticles.

Surface chemistry and in situ spectroscopy of a lysozyme langmuir monolayer

Surface pressure and surface potential-area isotherms were used to characterize a lysozyme Langmuir monolayer. The compression-decompression cycles and stability measurements showed a homogeneous and stable monolayer at the air-water interface. Salt concentration in the subphase and pH of the subphase were parameters controlling the homogeneity and stability of the Langmuir monolayer. In situ UV-vis and fluorescence spectroscopies were used to verify the homogeneity of the lysozyme monolayer and to identify the chromophore residues in the lysozyme. Optimal experimental conditions were determined to prepare a homogeneous and stable lysozyme Langmuir monolayer.